Process for electrolytically producing persulfates.



To all whom it may concern:

Be it known that GUSTAV TEICHNER and PAUL ASKENASY, have invented a Process for Electrolytically. Producing Persulfates, of-

which the folloWing'is a clear and true specification.

The present invention consists of a process for electrolytically producing 'persulfates, as hereinafter particularly set forth.

it isknown, that the output 'oftpersulfate depends in the first lace on the potential atv the anode. The big or this otential is,;the

greater is the output of persu ate. Byadd; ing very small quantities, of certain substances to. the ele'ctrolytd'the anodic potential and'cons'equently the output of ersulfatecan be considerably increased. 11 this respect the" ions Fl,,-Qlj )l O Cr 0, etc. have proved to be particuiarlyeffective.

-Now We have found thatthe advantageous effect of the above mentioned additions gradually disap ears and that the anodic potential as we as the output in persulfate considerably diminishes, when the electrolysis is of Ion duration. It was furtherdemonstrated that this decrease is due to the formation of the so called Caro acid (mono persulfur'ic acid) in the electrolyte. It is known thatthe p6ISl1lfat8S, Wh1l-.(liS

solved in stron sulfuric acid are gradu'ally convertedinto aaro acid and thatttliespeed of conversion increases With the degree "'of acidity. Thus. for instance, the amount of Caro acid contained in a saturated solution of sodium bisulfate and pe'r'sulfate at 15 C.

will increase about 0.3% in 24 hours. With a solution to which is added 10% of sulfuric acid, this-increase will rise, under otherwise similar circumstances to about 0.6% in 24 40. hours.

-VVe have found by experiments that the Caro acid is destroyed at the anode, oxygen being developed. 'The acid thus operatesasan anodic depolarizing agent; thus causing a l corresponding decrease in the outputs of the persul ate. NVhile, for instance, in the electrolysis of a saturated solution of sodium bisulfate containing 5% of perchlorate of sodium, the anodic oxidation amounts to about 70%, it immediately sinks to about/35% on adding 1% of Caro acid and down to about Specification of Letters Patent,

Application filed February 12,1906. Serial No. 300.652.

' formed.

e s'rAv TEICHNER AND PAUL ASKENASY, or NUREMBERG, GERMANY.

' PROCESS FOR- ELECTROLYTICALLY PRODUCING PERSULFATESV Patented March '3, 1908.

30 on adding 1% more of this acid. This difficulty can be obviated by destroying the Caro acid in the same proportion as it is stances are added to the electrolyte and since Caro acid at ordinary temperature is a much more owerful oxidizing a ent than ersulfuric' acid to be destroyed by such reducing substances.

Ifga reducing medium is added to a persulfate solution containing Caro acid, in proportion to the amount of the latter contained in thesolution,- the (Damned will be destroyed withoutiany loss of the persulfurlc acid. Various substances may be employed as reducing medium for the Caro acid. Eor theproduction of persulfate of sodium, sup fite or bisulfite of sodium, hydrochloric acid and common salt have proved to be the most suitable: The latter substances have a particularly favorable effect, since they simultaneously increase the anodic potential and consequently favorabl influence the oxidation; This is most e ectively carried For this purpose reducing sub-' it Will consequentl y be the rst out in-the following'manner:-The speed of formation of the Caro acid in an electrolyte of given concentration and acidity, is first determined once for all, and then in the course of electrolysis such quantities of the reducin substance are added, as are necessary or the reduction of this acld. An

excess of the reducing substance should be' avoided inorder to avoid the simultaneous destruction-of a part of the persulfate. If,-

-in consequence of an interruption of the electrolysis the electrolyte should contain" greater quantities of Caro acid, it may again e rendered fit for electrolysis by adding at once the calculated amount of the reducing saturated solution of bisulfate of sodium with the additionof 125 gr. or of per-' chlorate of sodium, are eleotrolyzed by a cur-' rent of 25 amp. at a temperature of 15 C;

'90 substance. As an examplez-25 liters of a 10 periodieally adding thereto, during the eloo- JOSEF ViiLKL.

68% and after eight days of uninterrupted trolysis reducing agents adapted to reduc electrolysis it wasstill 63%. The above proc the Caro-acid as it is formed. ess may of course be employed for the pro- In testimony whereof we eflix our signaduction of other persulfates in a corresponrltures in the presence of two Witnesses.

ing manner.

X We claim as our invention A process for producing persulfat es, which consistsin subjecting the solutions of the cor- Witnesses: responding sulfates'to eleetrolytrc action and TQPERNN HARTL, 

